Benchmarking ion-ion-orbit-following codes, SPIRAL and ASCOT5 on Toroidal Alfven Eigenmodes*

The ion-orbit-following codes SPIRAL and ASCOT5 are crucial tools for modeling energetic ion orbits, particularly fusion-generated alpha particles, in tokamak environments. Their prime function is to determine the proportion of alpha particles lost to the wall and evaluate the resultant surface heating, which can potentially induce wall melting. The two codes have been previously benchmarked against one another using expected conditions in the SPARC tokamak to assess particle losses, power losses, and ripple losses (JPP 86 (2020) 865860508) in MHD-quiescent plasmas. The results indicated a tolerable level of surface heating in the absence of MHD. This work extends the previous studies to include fast-ion redistributions triggered by Toroidal Alfven Eigenmodes (TAEs), which might instigate additional losses.  First, the two simulation codes will be benchmarked against one another in the presence of TAEs using an eigenmode structure computed by NOVA, over a range of assumed mode amplitudes. We will then quantify the magnitude and radial location of changes in the alpha density as a function of mode amplitude.  Finally, we intend to examine the patterns of resultant surface heating on SPARC due to the TAEs.